Photon gas

1. The problem statement, all variables and given/known data
1.Show that
[tex] PV^Y [/tex] is a constant for adiabatic,quassistatic expansion of a photongas and determine Y
2. Show the same for full degenerate gas of fermions at T=0

2. Relevant equations

3. The attempt at a solution1. The problem statement, all variables and given/known data